Process for separating wax from asphalt-wax mixtures



May 25, 1937. u. B. BRAY 2,081,733

PROCESS FOR SEPARATING WAX FROM ASPHALT-WAX MIXTURES OrigimilFiled. May 9, 1932 INVENTOR. Ulric 5. Bray ATTORNEY.

Patented May 25, 1937 raocsss FOR surname wax mom ASPHALT-WAX MIXTURES Ulric B. Bray, Palosyerdes-Estates, (JaliL, as-

signor to Union Oil Company of C alifornit,

,Los Anzeles, Calif., a corporation of California Original application May 9, 1932, Serial No.

Divided and this application Decembe! 8, 1933, Serial No. 701,497

' 9 Claims.

This invention relates to a process for the sepa ration of asphalt and wax from oil and for separating the asphalt from the wax. More specifically, it relates to a process for separating a mixture of asphalt and wax from oil by the use of solvents and then separating and resolving the mixture of asphalt and wax into separate fractions of asphalt and wax by the use of solvents. This application is a division of my copending application, Serial No. 610,130, filed May 9th, 1932 which is a continuation in part of my copending application, Serial No. 466,189, filed residue cannot be obtained by ordinary distillation means owing to the high boiling point of certain of the paraffin or wax members present. If a further separation of the wax from the overhead distillates is desired, this is accomplished by such processes as cold settling, cold pressing or the centrifuge methods which are well known to those skilled in the art.

In employing solvent extraction for the separation of oil from asphalt solvents may be used in which the oil is relatively soluble and in which I the asphalt is relatively insoluble. Thus, when naphtha, gasoline or even the lighter hydrocarbons, such as liquid butane, propane or ethane,

- are employed as selective solvents to separate asphalt from oil the asphalt being substantially insoluble in the foregoing solvents is left as a residue and the oils are separated from this insoluble residue as solutions dissolved in the foregoing respective solvents. Where wax is present in the asphaltic oil this materialis also separated in solution along with the solvent and oil. Providing it is desired to separate the wax from the oil and solvent this may be accomplished by chilling the solvent solution of oil by any appropriate means and then separating the precipitated wax by settling, filtering or centrifuging from the solvent solution of oil.

From the preceding description it can readily be seen that in order to separate oil from oil containing asphalt and wax two distinct separation steps must be employed. First the asphalt present must be separated from the oil and wax either by distillation or solvent extraction and secondly the waxy oil recovered from the distillation or solvent extraction step must be subjected (Ci. 1ii613) to dewaxing methods in order to separate the wax from the oil. I have discovered that it is unnecessary to separate 'oil from oil containing asphalt and wax by first separating the asphalt from the oil and wax and then separating the wax from the oil. I have found that asphalt and wax can be separated together or simultaneously from oils containing the same without some 01 the attending difllculties which are present in the two-step methods now employed and as described above. 7

When oil containing asphalt and wax is mixed with low molecular weight hydrocarbon solvents, suchas liquid propane, there occurs a substantially complete separation of the asphalt from the oil and wax present which dissolve in the liquidpropane. If now a portion of the liquid propane is allowed to vaporize under reduced pressure the mass is chilled to a temperature sufiiciently low to cause precipitation of the wax. The ebullition or boiling which accompanies the vaporization of the liquid propane causes a violent agitation of the mass and the small asphalt particles present offer themselves as nuclei for the agglomeration of the wax as it is precipitated .at the lower temperatures attained. After a temperature has been reached, which is sufficiently low to cause thorough precipitation and agglomeration of the wax present, further vaporization of the light hydrocarbon solvent is prevented by imposing suflicient pressure upon the surface of the liquid to prevent further boiling. The agglomerated particles of asphalt and wax may then be separated from the solvent solution of oil by any suitable means, such as settling, centrifuging or filtering. The oil dissolved in the solvent may be recovered by. distilling out the light hydrocarbon solvent.

Furthermore, I may commingle the oil containing asphalt and wax in liquid propane under reduced pressure to precipitate the asphalt and wax together, separate the precipitated asphalt and wax from the propane solution of oil and then separate the solvent from the oil. The propane under reduced pressure is precooled and causes a simultaneous separation of the asphalt and wax from the oil.

I may also employ wax anti-solvents in conjunction with my process to facilitate the separation of the wax. For example, a. suitable wax anti-solvent maybe dissolved in the liquid propane and this mixture may be ccmmingled with the oil containing asphalt and wax to separate the asphalt and wax from the oil. Usually where wax anti-solvents are employed the amount of refrigeration necessary to cause thorough wax precipitation is materially lessened and in some cases may be completely eliminated. As wax antisolvents I may employ methylene dichloride,

methyl formate, alcohol, acetone, mixtures of acetone and benzol, mixtures of methylene dichloride and benzol.

By the term propane, I intend to-include such hydrocarbons as are normally vaporous at ordinary pressure and temperature. carbons include methane, ethane, propane, butane, isobutane and mixtures thereof. These volatile solvents may be obtained by rectification of casing head gasoline by the so-called stabilizing method, now conventional in the natural gasoline industry. They are the overhead obtained. They are liquefied by compression and cooling in the conventional manner and drawn normal butane.

off into pressure chambers where they are maintained in a liquid state until used. A typical analysis of such a fraction is 6.72% ethane, 72.20% propane, 19.91% isobutane and 1.17%

Such a fraction may be maintained in a liquid state at a pressure of 125 pounds per square inch and a temperature of about 75 F. The predominating hydrocarbon member in this mixture is propane.

I have also discovered that I may separate the wax from the precipitated asphalt-wax mixture. This may be accomplished by washing the mixture with the light hydrocarbon solvent at normal temperature to dissolve the wax from the asphalt. The wax is then recovered from the hydrocarbon solution by distilling away the hydrocarbon solvent, or by refrigerating the solution and precipitating the wax therefrom.

My process finds application in production of lubricating oil and especially in conjunction with Mid-Continent or California crudes where there is a considerable quantity of asphalt and wax present in the oil. However, it is not restricted to the production of lubricating oil as it may be employed in conjunction with any on where it is desirable to obtain a separation of the oil fro the asphalt and wax.

It is, therefore, an object of my invention to coprecipitate asphalt and wax from oil containing these materials. It is another object of my invention to separate asphalt and wax together from oil containing asphalt and wax by the use of solvents in which the oil is relatively soluble and the asphalt and wax relatively insoluble.

' It is a particular object of my invention to sep arate the wax from the coprecipitated asphaltwax mixture. Specifically, I desire to separate the wax from the asphalt-wax mixture by washing the mixture with a light hydrocarbon solvent by refrigeration to precipitate the wax from the solution.

Figure 1 is illustrative of one formof apparatus 7 in which I may carry out my process.

Referring more particularly to the drawing, oil containing asphalt and wax in tank I is withdrawn through valve 2 and line 3 to pump 4 which forces it through line 5 into agitator 6 where it is mixed with a stream of liquid propane coming from tank 9 through line 60, valve II, pump 12 and line l3. After thorough agitation of the oil'and liquid propane in agitator 6, the mass passes through line 1 into chiller 8 where the temperature of the mass 'is lowered sumciently to complete thorough precipitation of the wax by allowing a portion of the liquid propane to vaporize through valve l4, line 62 into compressor l5 which forces it through line ii .to

Such hydrocondenser I! where it is liquefied and passes by means of line l8 into propane storage tank 9.

During the chilling operation in chiller 8 sufiicient agitation is produced by the boiling liquid to cause intimate contact between the small precipitated asphalt'particles and the precipitated wax. The asphalt particles function as nuclei to agglomerate the precipitated wax. The agglomerated mixture of asphalt and wax along with the propane solution of oil is removed through line I9, valve 20 and line 2| to pump 22 which forces it through line 23 into filter press 24 where the agglomerated asphalt and wax is separated from the propanesolution of oil.

Propane solution of oil is removed from filter press 24 through valve 25 to pump 26 which forces it through line 21 into vaporizer 28 where, by the aid of heat, propane is vaporized from the oil and passes by means of valve 33 to compressor 34 which forces it through line 35 and line l6 to condenser II where it is liquefied and passes by means of line i8 into propane storage tank 9. The oil free from asphalt and wax is removed from vaporizer 28 throughvalve 30 and line 3! to storage tank 32.

The agglomerated mixture of asphalt and wax passes by means of line 36 into agitator 31 where it is thoroughly washed with liquid propane coming from tank 9 through line 60, valve I0, pump 6] and line 64. The thoroughly washed mixture of asphaltand wax passes from agitator 31 by means of line 38 into settling chamber 39 where the insoluble asphalt settles out and is removed through valve 40 to pump 4| which forces it through line 42 into heater 43 where the temperature of the mass is raised sufiiciently high to vaporize all the propane present. The heated mass passes from heater 43 through line 44 into separator 45 where the molten asphaltic material is removed through valve 46 and line 52 where the propane is vaporized, aided by,

steam circulating through closed coil 53. The vaporized propane is withdrawn via line 61 controlled by valve 65 and pump 56 and passed to condenser 11, linei 8 into propane storage tank 9. The'wax is withdrawn from the bottom of the vaporizer 52 and passed via line controlled by valve 54 into storage tank 56.

As an example of the preferred method of carrying out my process, crude oil containing wax produced from the Santa Fe Springs field, Cali,- fornia, is distilled to separate, all of the light fractions present, such as gasoline, kerosene and gas oil. The residuum having a gravity at F. of 21.1 and a Saybolt universal viscosity of 280 seconds at 210 F. is withdrawn from tank I and mixed in line 5 with about 4 volumes of propane 'withdrawn from tank 9. This is suflicient to 'wax and this results in an agglomeration of these two materials. The chilled mass is then withdrawn from the chilling chamber 9 and passes to filterpress 24 where the precipitated asphalt and wax is separated from the propane solution of oil. The propane solution of oil passes to vaporizer 28 where the propane is vaporized and sent back to storage tank 9 and the asphalt and wax-free oil passes to tank 32.

The asphalt and wax mixture is removed from filter 2E and passesinto line 36 where it is mixed with propane in the proportion of one volume of the asphalt-wax mixture to three volumes of propane. This mixture then passes to agitator 3? where it is thoroughly agitated, after which the mass passes to settling chamber 39 where the asphalt is withdrawn and sent to the means shown for distilling air the propane from the asphalt. The propane solution of wax passes from settling chamber-39 to vaporizer 52 where the propane is vaporized and returned to storage tank 9 via line 6'! controlled by valve 65, pump 66, condenser ii and line H3. The wax is withdrawn from the bottom of v'aporizer 52 and passed via line 55 controlled by valve 54 into storage tank 56.

The above description is not to be taken as limiting, but merely as illustrative of one mode of carrying out my process, as many variations taining a majorportion of propane to dissolve the wax but to leave the asphalt as an undissolved .fraction and separating the wax solution of phalt and wax to leave an asphalt-wax mixture containing a minor portion of oil, commingling said asphalt-wax mixture with a liquefied normally gaseous hydrocarbon containing a major portion of propane at a. temperature sufiicient to x dissolve the wax but to leave the asphalt as an undissolved fraction and removing the asphalt y from the solvent solution of wax.

dissolved fraction and removing the asphalt from I the solvent solution of wax.

7. A. process for the separation of asphalt and waxfrom oil which comprises commingling said oil with liquid propane to dissolve the oil and wax and to precipitate asphalt, cooling the oil commingled with said liquid propane in the pres-' ence of the precipitated asphalt to precipitate wax, removing the mixture of precipitated asphalt and wax from the oil dissolved in liquid propane, commingling the mixture of precipitated asphalt and wax with a further quantity of said liquid propane at a temperature suflicient to dissolve the wax but to leave the asphalt asan undissolved fraction and removing the asphalt from the liquid propane solution of wax.

8. A process for the separation of asphalt and wax from oil which comprises commingling said liquefied normally gaseous hydrocarbon solvent from the'asphalt.

2. A process for the separation of asphalt from asphalt-wax mixtures which comprises commingling said asphalt-wax mixture with a liquefied normally gaseous hydrocarbon solvent containing a major portion of hydrocarbon having less than 4 carbon atoms to dissolve the wax but to leave the asphalt as an undissolved fraction and separating the wax solution of liquefied normally gaseous hydrocarbon solvent from the asphalt.

4. A process for the separation of asphalt from the asphalt-wax mixture which comprises commingling said asphalt-wax mixture with liquid propane to dissolve the wax but to leave the asphalt as an undissolved fraction and separating the wax solution of liquid propane from the asphalt.

4. A process for the treatment of oil containing asphalt and wax'which comprises separating a major portion of oil from the oil containing as oil with a liquefied normally gaseous hydrocarbon containing a major portion of propane to dissolve the oil and wax and to precipitate asphalt, cooling the oil commingled with said liquefied normally gaseous hydrocarbon in the presence of the precipitated asphalt to precipitate wax, removing the mixture of precipitated asphalt and wax from the oil dissolved in said liquefied normally gaseous hydrocarbon, commingling the mixture of precipitated asphalt and wax with a further quantity of said liquefied normally gaseous hydrocarbon at a temperature sufficient to dissolve the wax but to leave the asphalt as an undissolved fraction and-"removing, the asphalt from the liquefied normally gaseous hydrocarbon solution of wax.

9. A process for the separation of asphalt and wax from oil which'comprises commingling said oil with a liquefied normally gaseous hydrocarthe wax but to leave the asphalt as an undissolved fraction and removing the asphalt from the liquefied normally gaseous hydrocarbon solution of wax.

' ULRIC B. BRAY.. 

